Demonstration of organ differences in peripheral B cell populations through the use of deficient fetal bovine serum

Deficient fetal bovine serum (FBS) was used in culture to distinguish differences in the B cell populations of peripheral lymphoid organs. Culture medium supplemented with deficient FBS supported the induction of primary humoral immune responses to heterologous erythrocyte antigens in murine Peyer's patch and lymph node cultures, but not in spleen cultures obtained from the same unimmunized mice. This difference was not due to a difference in thymus-derived (T) cell or adherent cell activity, or to the production of stimulating factors by Peyer's patch or lymph node cells. In view of the finding that spleen cells from mice immunized with erythrocyte antigens support immune responses in deficient FBS, we suggest that murine Peyer's patches and lymph nodes contain antigen-experienced B cells, whereas spleens contain predominately antigen-inexperienced B cells. In contrast, spleen and Peyer's patch cells cultured with deficient FBS can be induced to mediate specific cytotoxic allograft responses which are similar in magnitude to responses observed in normal FBS. Deficient FBS may provide a useful tool for distinguishing between B cells on the basis of prior antigenic encounter, and for examining the induction of T cell responses in the absence of B cell responses.